Array speaker system

ABSTRACT

In an array speaker system that performs multi-channel reproduction using an array speaker constituted by arraying a plurality of speaker units in a matrix manner, a left channel signal, a right channel signal, and a center channel signal, all of which instruct reproduction of sound at a front side of a listener, are subjected to weighting using weight coefficients based on a Bessel function so as to drive the speaker units, thus realizing spherical sound emission characteristics. In addition, a surround left channel signal and a surround right channel signal, both of which instruct reproduction of sound at a rear side of the listener, are subjected to beam processing, whereby sound is reflected on a sound reflection position such as a wall surface or a ceiling and is then emitted in the form of a sound beam reaching the rear side of the listener.

TECHNICAL FIELD

This invention relates to array speaker systems in which a plurality ofspeaker units are arranged in an array.

BACKGROUND ART

Conventionally, array speaker systems in which a plurality of speakersare regularly arranged so as to reproduce sounds are known. In thesearray speaker systems, as a form of trouble due to the use of pluralspeakers, there occurs a phenomenon in which as reproduced audiofrequencies become higher, so-called beam-like concentration of soundand comb-like distribution of sound (in which sound is spread in acomb-shape manner) emerge in sound emission characteristics, which varyin response to frequencies and which make it difficult to realizehearing of prescribed tone pitches outside of a sound emission centerposition, or in which audio frequency characteristics greatly vary inresponse to listening positions.

FIGS. 9A and 9B are three-dimensional graphs showing simulation resultsregarding sound emission characteristics when fifteen speaker units arelinearly arrayed and are each driven to emit sound with the same weight(i.e., weight coefficient “1”). Herein, FIG. 9A shows sound emissioncharacteristics upon emission of a signal of an audio frequency of 1 kHzin a horizontal cross-sectional plane, a vertical cross-sectional plane,and a projection plane, which is 2 m distant from the front surface ofthe speaker system. FIG. 9B shows sound emission characteristics uponemission of a signal of an audio frequency of 10 kHz. They show thatsound pressure becomes higher in white areas.

As shown in FIGS. 9A and 9B, beam-like concentration of sound occurs insound emission characteristics in the vertical cross-sectional plane,wherein as the audio frequency becomes higher, the comb-likedistribution of sound apparently occurs. Such sound is not preferable interms of the sense of hearing; in addition, it is impossible to hearsounds of specific audio frequencies outside of the position in whichthe beam-like concentration of sound occurs; and this causes a problemin that the listening position is extremely limited. Incidentally,sectorial sound emission characteristics occur in the horizontalcross-sectional plane.

In order to avoid the occurrence of the aforementioned phenomenon, aso-called Bessel array method, in which a string of regularly arrangedspeakers are driven with weights using a string of coefficients based ona first-order Bessel function so as to realize spherical sound emissioncharacteristics, is known. In this method, a plurality of speaker units,which are linearly arranged with prescribed distances therebetween, aredriven to emit sound signals, which are weighted by use of weightcoefficients based on the first-order Bessel function represented by thefollowing equation.${J_{n}(x)} = {\left( \frac{x}{2} \right)^{n}{\sum\limits_{k = 0}^{\infty}\frac{\left( {- 1} \right)^{k}\left( {x/2} \right)^{2k}}{{k!}{\Gamma\left( {n + k + 1} \right)}}}}$

Similarly to FIGS. 9A and 9B, FIGS. 10A and 10B show simulation resultsregarding sound emission characteristics of a Bessel array in whichfifteen speaker units are linearly and vertically arranged and aredriven by use of signals, which are weighted based on the first-orderBessel function. Herein, FIG. 10A shows sound emission characteristicsupon emission of a signal of an audio frequency of 1 kHz in a horizontalcross-sectional plane, a vertical cross-sectional plane, and aprojection plane, which is 2 m distant from the front surface of thespeaker system. FIG. 10B shows sound emission characteristics uponemission of a signal of an audio frequency of 10 kHz.

Incidentally, J⁻⁷(x) to J₇(x) are used as weight coefficients adapted tospeaker units, wherein when x=3.0, coefficients C1 to C15, which areused for multiplication with respect to signals driving fifteen speakerunits, are calculated as follows:

-   -   C1=J⁻⁷(3)=−0.0025    -   C2=J⁻⁶(3)=0.0114    -   C3=J⁻⁵(3)=−0.0430    -   C4=J⁻⁴(3)=0.1320    -   C5=J⁻³(3)=−0.3091    -   C6=J⁻²(3)=0.4861    -   C7=J⁻¹(3)=−0.3391    -   C8=J₀(3)=−0.2601    -   C9=J₁(3)=0.3391    -   C10=J₂(3)=0.4861    -   C11=J₃(3)=0.3091    -   C12=J₄(3)=0.1320    -   C13=J₅(3)=0.0430    -   C14=J₆(3)=0.0114    -   C15=J₇(3)=0.0025

It is obvious that through the comparison between FIGS. 9A and 9B andFIGS. 10A and 10B, in the case of the Bessel array, no beam-likeconcentration of sound or comb-like distribution of sound occurs in thesound emission characteristics, thus realizing substantially sphericalcharacteristics. As described above, by driving speaker units withweights corresponding to weight coefficients, it is possible toeffectively avoid the occurrence of beam-like concentration of sound andcomb-like distribution of sound in sound emission characteristics.

Japanese Examined Patent Application Publication No. H01-25480 disclosesa speaker system adopting a simplified form of the aforementioned Besselarray.

When sound emitted from an array speaker is reflected on a wall surfaceand a ceiling so as to realize surround effect, characteristics of thearray speaker in which emitted sound is easily subjected to beam-likeconcentration may work desirably. However, there is a problem in thatthe listening position is limited with respect to a tone-generationchannel regarding sound emission in front of the listener.

It is an object of this invention to provide an array speaker system inwhich by effectively using characteristics of an array speaker, in whichbeam-like concentration of sound easily occurs, and the properties of aBessel array, which realize spherical sound emission characteristics,both of the front-side sound and rear-side sound produced by the arrayspeaker can be reproduced desirably.

DISCLOSURE OF THE INVENTION

An array speaker system of this invention is constituted by arraying aplurality of speaker units, each of which inputs a front-side channelsignal for instructing generation of sound reproduced at a front side ofa listener and a rear-side channel signal for instruction generation ofsound reproduced at a rear side of the listener. Herein, speaker unitsare each driven by use of a front-side channel signal that is weightedusing weight coefficients based on a Bessel function; and the speakerunits are each driven by use of a rear-side channel signal that issubjected to prescribed delay processing so as to form a sound beam,which is reflected on a wall surface and a ceiling and then reaches therear side of the listener.

The aforementioned array speaker system can be constituted by use of afirst array speaker, which is arranged at the left side of a display,and a second array speaker, which is arranged at the right side of thedisplay, for example.

With respect to the first array speaker arranged at the left side of thedisplay, a left-channel signal and a center-channel signal are weightedusing weight coefficients based on a Bessel function; and a surroundleft-channel signal is subjected to beam processing. With respect to thesecond array speaker arranged at the right side of the display, aright-channel signal and a center-channel signal are weighted usingweight coefficients based on a Bessel function; and a surroundright-channel signal is subjected to beam processing.

When the array speaker system is constituted by use of an array speakerarranged at the front side of a listener, front-side channel signals,i.e., a center-channel signal, a left-channel signal, and aright-channel signal, are respectively weighted using weightcoefficients based on a Bessel function; and rear-side channel signals,i.e., a surround left-channel signal and a surround right-channelsignal, are subjected to beam processing.

Furthermore, when the array speaker system is constituted by use ofarray speakers that are arranged in a matrix manner, speaker units aredriven by use of signals, which instruct reproduction of sounds at setuplocations of the array speakers and which are respectively weightedusing weight coefficients based on a Bessel function. In addition,speaker units are driven by use of signals, which instruct reproductionof sounds at specific positions outside of setup locations of arrayspeakers and which are subjected to delay processing so as to form soundbeams reaching the specific positions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing the exterior appearance of an arrayspeaker system in accordance with a first embodiment of this invention;

FIG. 2 diagrammatically shows a sound field realized by multi-channelreproduction in the array speaker system shown in FIG. 1;

FIG. 3 is a circuit diagram showing the constitution of a drive circuitfor driving a plurality of speaker units constituting the array speaker;

FIG. 4 show examples of weight coefficients, which are used for theweighting based on a Bessel function and which are respectively appliedto input signals of the speaker units constituting the array speaker;

FIG. 5 is an illustration for explaining a setup method of a delay valueapplied to a surround channel signal;

FIG. 6 is a front view showing the exterior appearance of an arrayspeaker system in accordance with a second embodiment of this invention;

FIG. 7 is a circuit diagram showing a drive circuit for driving aplurality of speaker units included in the array speaker system shown inFIG. 6;

FIG. 8 is an illustration for explaining an array speaker system inaccordance with a third embodiment of this invention;

FIG. 9A shows sound emission characteristics of an array speaker withrespect to an audio frequency of 1 kHz;

FIG. 9B shows sound emission characteristics of an array speaker withrespect to an audio frequency of 10 kHz;

FIG. 10A shows sound emission characteristics of a Bessel array withrespect to an audio frequency of 1 kHz; and

FIG. 10B shows sound emission characteristics of a Bessel array withrespect to an audio frequency of 10 kHz.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows the exterior appearance of an array speaker system inaccordance with a first embodiment of this invention. Reference numerals1 and 2 designate array speakers, each of which has m×n speaker unitsarrayed in m rows and n columns (where m and n are integers of 2 ormore); and reference numeral 3 designates a display having a screen or alarge-size display screen. Herein, m is set to an integer of 6 or more,and n is set to an integer of 5 or more, whereby each of the arrayspeakers 1 and 2 is preferably formed in a vertically elongated shape.That is, in the present embodiment, the first array speaker 1 and thesecond array speaker 2, each of which has a vertically elongated shape,are arranged at the left side and the right side of the display 3; thus,it is possible to realize a superior design.

FIG. 2 diagrammatically shows a sound field realizing multi-channelreproduction using the array speaker system of the first embodimentshown in FIG. 1. It performs 5.1 channel reproduction, for example. FIG.2 is an illustration of a listening room in a plan view, whereinreference numeral 4 designates a listener; reference numeral 5designates a left-side wall surface; reference numeral 6 designates arear-side wall surface; and reference numeral 7 designates a right-sidewall surface.

As shown in FIG. 2, in the first embodiment of this invention,reproduction for a main left channel (L), a center channel (C), and asurround left channel (SL) is allocated to the first array speaker 1arranged at the left side of the display 3; and reproduction for a mainright channel (R), a center channel (C), and a surround main rightchannel (R) is allocated to the second array speaker 2 arranged at theright side of the display 3.

A Bessel array method in which the array speakers 1 and 2 are eachdriven with weights corresponding to weight coefficients based on aBessel function is applied to the three channels lying in front of thelistener 4, i.e., the aforementioned channels C, L, and R, whereby it ispossible to realize spherical sound emission characteristics as shown inFIG. 2.

With respect to the SL channel and the SR channel for the rear side ofthe listener 4, sound beams emitted from the array speakers 1 and 2respectively are reflected on prescribed walls and ceiling so as to makeit possible for the listener 4 to hear sound virtually emitted from therear side. That is, the sound beam of the SR channel emitted from thefirst array speaker 1 is firstly directed to the left-side wall surface5; then, it is reflected on the wall surface 5; next, it is reflected onthe ceiling (not shown); furthermore, it is reflected on the rear-sidewall surface 6; thereafter, it reaches the rear-left portion of the headof the listener 4. The sound beam of the SR channel emitted from thesecond array speaker 2 is firstly directed to the right-side wallsurface 7; then, it is reflected on the wall surface 7, ceiling, andwall surface 6 in turn; thereafter, it reaches the rear-right portion ofthe head of the listener 4.

As described above, in the present embodiment, it is possible to realizespherical sound emission characteristics with respect to the threechannels in front of the listener 4, i.e., the channels L, R, and C;hence, it is possible to realize natural audio reproduction withoutcausing limitation to listening position. In addition, components ofsound beams are effectively used with respect to the surround channelsSL and SR regarding the rear side of the listener 4; hence, it ispossible to realize audio reproduction at the rear side of the listener4.

Next, a circuit constitution for driving the array speakers 1 and 2 willbe described.

In FIG. 3, reference numerals 1-11 to 1-mn designate speaker units ofm×n array forming the first array speaker 1; and reference numeral 11designates an A/D converter (ADC) for converting signals of the centerchannel (C) into digital data. Reference numerals 12-1 to 12-mndesignate weighting means that are respectively arranged for the speakerunits 1-11 to 1-mn so as to impart weights using weight coefficientsCC11 to CCmn based on a Bessel function to the center-channel signals.Reference numeral 13 designates an A/D converter (ADC) for convertingsignals of the main left channel (L) into digital data. Referencenumerals 14-11 to 14-mn designate weighting means that are respectivelyarranged for the speaker units 1-11 to 1-mn so as to impart weightsusing weight coefficients CL11 to CLmn based on a Bessel function to theL-channel signals. Reference numeral 15 designates an A/D converter(ADC) for converting signals of the surround left channel (SL) intodigital data. Reference numerals 16-11 to 16-mn designate delay meansthat are respectively arranged for the speaker units 1-11 to 1-mn so asto apply the corresponding delay values to the LS-channel signals, thusrealizing beam-like concentration of sound in the surround left channeldirection.

Reference numerals 17-11 to 17-mn designate adders that are respectivelyarranged for the speaker units 1-11 to 1-mn so as to add output signalsof the weighting means 12-11 to 12-mn, output signals of the weightingmeans 14-11 to 14-mn, and output signals of the delay means 16-11 to16-mn together. Output signals of the adders 17-11 to 17-mn areconverted into analog signals in D/A converters (DAC) 18-11 to 18-mn;furthermore, they are amplified in power amplifiers 19-11 to 19-mn;thereafter, they are supplied to the speaker units 1-11 to 1-mnrespectively.

As described above, addition signals that are produced by adding the Cchannel signals and L channel signals weighted based on the Besselfunction to the SL channel signals applied with prescribed delay valuesare supplied to the speaker units 1-11 to 1-mn constituting the firstarray speaker 1 as its drive signals.

Illustration is not provided herein, but it is possible to provideamplifiers for adjusting gains of the signals of the respective channelswith respect to the speaker units. That is, it is possible toadditionally provide amplifiers for adjusting gains of the signals forthe speaker units prior to the weighting means 12-11 to 12-mn, prior tothe weighting means 14-11 to 14-mn, or prior to the delay means 16-11 to16-mn.

In addition, the same circuit constitution as the circuit constitutionof FIG. 3 arranged for the first array speaker 1 is arranged for thesecond array speaker 2. That is, the circuit constitution of FIG. 3 canbe modified as shown in the reference symbols in parentheses so as torealize the circuit constitution for the second array speaker 2, whereinthe L channel is replaced with the R channel, and the SL channel isreplaced with the SR channel.

In the circuit constitution of FIG. 3, signals of respective channelsare converted into digital data in the A/D converters (ADC) 11, 13, and15; then, the digital data are subjected to weighting and delayprocessing; thereafter, they are added together, but it is possible toperform signal processing in an analog manner without performingdigitization. That is, analog signals can be directly subjected toweighting, delaying, and adding, whereby it is possible to omit the A/Dconverters (ADC) 11, 13, and 15 as well as the D/A converter (DAC) 18.Alternatively, it is possible to use digital amplifiers for thereplacement of the amplifiers (AMP) 19 by omitting only the D/Aconverter (DAC) 18.

FIG. 4 shows examples of weight coefficients based on a Bessel function,which are applied to the weighting means 12-11 to 12-mn and the weighingmeans 14-11 to 14-mn respectively.

It is described in conjunction with FIGS. 10A and 10B that when weightsbased on a Bessel function are applied to speaker units that arelinearly arrayed in an array speaker, sound emission characteristics inthe vertical cross-sectional plane have a spherical shape (or a circularshape). In the present embodiment in which the array speaker isconstituted using the speaker units 1-11 to 1-mn arrayed in m rows and ncolumns, weights based on a Bessel function are applied in both the rowdirection and column direction, thus realizing spherical sound emissioncharacteristics.

FIG. 4 shows examples of weight coefficients respectively applied to m×nspeaker units 1-11 to 1-mn where m=15, n=5. Herein, weight coefficientsof J⁻⁷(x1), J⁻⁶(x1), J⁻⁴(x1), J⁻³(x1), J⁻²(x1), J⁻²(x1), J₀(x1), J₁(x1),J₁(x1), J₃(x1), J₄(x1), J₅(x1), J₆(x1), and J₇(x1) are used for fifteenspeaker units vertically aligned; and weight coefficients J⁻²(x2),J⁻¹(x2), J₀(x2), J₁(x2), and J₂(x2) are used for five speaker unitshorizontally aligned. That is, weights corresponding to products of thevertical-alignment weight coefficients J_(k)(x1) (where k=−7, −6, −5,−4, −3, −2, −1, 0, 1, 2, 3, 4, 5, 6, 7) and the horizontal-alignmentweight coefficients J₁(x2) (where k=−2, −1, 0, 1, 2) are applied tospeaker units 1-ij (where i=1 to m, j=1 to n). Thus, it is possible torealize spherical sound emission characteristics.

It is possible to use the same weight coefficient for both the L-channelsignal and the C-channel signal; alternatively, it is possible to usedifferent weight coefficients using different parameters x1 and x2. Inaddition, it is possible to use weight coefficients, which are similarlydetermined, with respect to the second array speaker 2.

Delay values applied to the delay means 16-11 to 16-mn with respect tosignals of the surround left channel (SL) will be described withreference to FIG. 5.

In FIG. 5, reference numerals 1-1 to 1-n designate n speaker units thatare arrayed in a single line. In order to realize a sound beam (i.e., aconcentrated flow of acoustic waves) focusing on a prescribed position Xwith respect to a string of speaker units, a circle Y is drawn about thefocal point X to pass a far-most speaker unit (i.e., a speaker unit1-n); then, with respect to intersecting points at which line segmentsconnecting between the focal point X and the speaker units 1-1 to 1-nintersect the circle Y, distances Li (where i=1, 2, . . . , n) from thespeaker units are each divided by the speed of sound, thus producingdelay times with respect to the speaker units respectively. This makesit possible for sounds emitted from the speaker units 1-1 to 1-n toreach the focal point X with the same phase, wherein the focal point Xserves as a virtual sound source. Suppose that an angle of the soundbeam reaching the focal point X is identical to an angle of the soundbeam reaching the left-side wall surface 5 in FIG. 2; and the distancefor the focal point X is identical to the distance for the setupposition of the surround left channel (SL) speaker in FIG. 2. In thiscase, the listener hears the sound as if the sound of the SL channelwere emitted from the SL-channel speaker positioned at the focal pointX. With respect to the surround right channel (SR), the second arrayspeaker 2 arranged at the right side is controlled to emit a sound beamas described above.

An example in which a plurality of speaker units 1-1 to 1-n are arrayedin a one-dimension manner is described in conjunction with FIG. 5, butthe aforementioned array speakers 1 and 2 are arranged in atwo-dimensional manner. Therefore, the circle Y is replaced with asphere drawn about the focal point X; hence, delay times, which areproduced by dividing distances between the speaker units and thespherical surface by the speed of sound, are applied to the speakerunits.

In order for a sound beam emitted from the array speaker 1 or 2 to reachthe wall surface 5 or 7 with a prescribed angle, it is preferable to setthe number n of the speaker units in the columnar alignment to 5 ormore.

As described above, in the present embodiment, sound beams emitted fromthe array speakers are reflected on the wall surfaces and ceiling so asto realize the surround channel sound that is transmitted to thelistener at the rear side. That is, it is possible to effectively usecharacteristics of the array speaker in which sound is transformed intoa beam.

The first embodiment describes the array speaker system constituted bythe first array speaker arranged at the left side of the display 3 andthe second array speaker 2 arranged at the right side of the display 3.This invention is not necessarily limited to an array speaker systemhaving a divided arrangement of speakers.

FIG. 6 shows the exterior appearance of an array speaker system inaccordance with a second embodiment of this invention.

In FIG. 6, the array speaker system of the second embodiment isconstituted by a plurality of speaker units 21-11 to 21-jk, which arearrayed in j rows and k columns. Herein, it is preferable that j and kbe set to integers of five or more.

FIG. 7 is a circuit diagram showing the constitution of a drive circuitfor driving the array speaker system of the second embodiment shown inFIG. 6.

In FIG. 7, reference numerals 22-11 to 22-jk designate multipliers thatare respectively provided in connection with the speaker units 21-11 to21-jk so as to apply prescribed gains to signals of the aforementionedcenter channel (C). Reference numerals 23-11 to 23-jk designateweighting means for applying weight coefficients based on a Besselfunction to the C-channel signals.

Reference numerals 24-11 to 24-jk designate multipliers that areprovided in connection with the speaker units 21-11 to 21-jkrespectively so as to apply prescribed gains to the L-channel signals.In addition, reference numerals 25-11 to 25-jk designate weighting meansfor applying weight coefficients based on a Bessel function to theL-channel signals.

Reference numerals 26-11 to 26-jk designate multipliers that areprovided in connection with the speaker units 21-11 to 21-jkrespectively so as to apply prescribed gains to the R-channel signals.In addition, reference numerals 27-11 to 27-jk designate weighting meansfor applying weight coefficients based on a Bessel function to theR-channel signals.

Reference numerals 28-11 to 28-jk designate multipliers that areprovided in connection with the speaker units 21-11 to 21-jkrespectively so as to apply prescribed gains to the SL-channel signals.In addition, reference numerals 29-11 to 29-jk designate delay meansthat apply prescribed delay values to the speaker units 21-11 to 21-jkin order to form a sound beam in response to the SL-channel signals.

Reference numerals 30-11 to 30-jk designate multipliers that areprovided in connection with the speaker units 21-11 to 21-jkrespectively so as to apply prescribed gains to the SR-channel signals.In addition, reference numerals 31-11 to 31-jk designate delay meansthat apply prescribed delay values to the speaker units 21-11 to 21-jkin order to form a sound beam in response to the SR-channel signals.

Reference numerals 32-11 to 32-jk designate adders that add togetheroutput signals of the weighing means 23-11 to 23-jk regarding theC-channel signals, output signals of the weighting means 25-11 to 25-jkregarding the L-channel signals, output signals of the weighting means27-11 to 27-jk regarding the R-channel signals, output signals of thedelay means 29-11 to 29-jk regarding the SL-channel signals, and outputsignals of the delay means 31-11 to 31-jk regarding the SR-channelsignals. Reference numerals 33-11 to 33-jk designate amplifiers thatrespectively amplify output signals of the adders 32-11 to 32-jk so asto supply them to the speaker units 21-11 to 21-jk.

In the array speaker system of the second embodiment having theaforementioned constitution, three-channel signals in front of thelistener, i.e., C-channel signals, L-channel signals, and R-channelsignals, are respectively weighted using weight coefficients based on aBessel function, whereby the speaker units 21-11 to 21-jk emit sounds ina Bessel-array-like manner. In addition, with respect to surroundsignals at the rear side of the listener, i.e., SL-channel signals andSR-channel signals, the speaker units 21-11 to 21-jk emit desired soundbeams.

In addition, the multipliers 22-11 to 22-jk, 24-11 to 24-jk, 26-11 to26-jk, 28-11 to 28-jk, and 30-11 to 30-jk are provided to set up gainsfor the speaker units 21-11 to 21-jk with respect to signals of the Cchannel, L channel, R channel, SL channel, and SR channel. Herein, themultipliers 24-11 to 24-jk, which are provided to apply gains to thespeaker units 21-11 to 21-jk with respect to the L-channel signals,increase gains for the speaker units arrayed at the left-half side butdecrease gains for the speaker units arrayed at the right-half sidewithin the speaker units arrayed in a two-dimensional manner, forexample. In addition, the multipliers 26-11 to 26-jk, which are providedto apply gains to the speaker units 21-11 to 21 -jk with respect to theR-channel signals, increase gains for the speaker units arrayed at theright-half side but decrease gains for the speaker units arrayed at theleft-half side within the speaker units arrayed in a two-dimensionalmanner, for example.

In the second embodiment compared with the first embodiment shown inFIG. 1, it is possible to increase the number of speaker units arrayedin a column direction; hence, it is possible to reliably and adequatelyperform beam control in a horizontal direction; thus, it is possible toreproduce sounds of rear-side surround channels with good fidelity.

Incidentally, the aforementioned description is made with respect to the5.1 channel surround system, which is an example of multi-channelreproduction; however, this invention is not necessarily so limited toand is similarly applicable to other multi-channel reproduction using7.1 channels, for example.

Applied fields of this invention are not necessarily limited tomulti-channel reproduction; hence, it is possible to perform audioreproduction using a Bessel array at the setup position of an arrayspeaker and to perform audio reproduction using sound beams at anotherposition.

Next, a third embodiment in which this invention is applied to an audioreproduction system other than one effecting multi-channel reproductionwill be described with reference to FIG. 8.

In FIG. 8, reference numeral 41 designates an array speaker that isconstituted similarly to in the foregoing embodiments; and referencenumeral 42 designates a ceiling to which the array speaker 41 is fixed.

In the third embodiment, speaker units are driven by use of signals,which are weighted based on a Bessel function, at a position A entirelycovering the whole space of a room in which the array speaker 41 isfixed to the ceiling 42. In addition, sound beams are emitted to focuson a certain position such as a comer B of the room other than the setupposition of the array speaker 41 by use of delayed signals. Thus, by useof the array speaker 41, it is possible to emit prescribed soundthroughout the entirety of the room; and it is possible to emit soundbeams towards a specific position such as the comer B of the room, forexample. In this case, it is possible to emit reproduced sounds towardsthe positions A and B by use of the same signal; alternatively, it ispossible to emit sounds reproduced by use of different signals.

As described heretofore, the array speaker system of this invention hasa variety of effects and technical features as follows:

-   (1) With respect to front-side channels of the array speaker, a    Bessel array is used to reproduce natural and spherical sound waves.    With respect to rear-side channels, sound beams are reflected on the    wall surfaces and ceiling so as to reproduce desired sound at the    rear side of the listener.-   (2) A Bessel array is used to reproduce sound at the setup position    of the array speaker; and sound beams are reproduced with respect to    another position. Hence, natural and spherical sound waves can be    reproduced at the position of the array speaker; and desired sound    can be localized at a desired position.

Incidentally, this invention is not necessarily limited to theaforementioned embodiments; hence, this invention embraces all changeswithin the scope of the invention as defined in the appended claims.

1. An array speaker system constituted by arraying a plurality ofspeaker units, said array speaker system comprising: a means forinputting front-side channel signals for instructing reproduction ofsound at a front side of a listener and rear-side channel signals forinstructing reproduction of sound at a rear side of the listener; ameans for driving the speaker units with weights using weightcoefficients based on a Bessel function with respect to the front-sidechannel signals; and a means for driving the speaker units with respectto the rear-side channel signals in such a way that sound is reflectedat at least one sound reflection position such as a wall surface or aceiling and is then applied with a prescribed delay value so as to forma sound beam reaching the rear-side of the listener.
 2. An array speakersystem according to claim 1, which is constituted by a first arrayspeaker arranged at a left side of a display and a second array speakerarranged at a right side of the display.
 3. An array speaker systemaccording to claim 2, wherein the front-side channel signals are formedusing a left channel signal, a right channel signal, and a centerchannel signal, and the rear-side channel signals are formed using asurround left channel signal and a surround right channel signal, andwherein in the first array speaker arranged at the left side of thedisplay, the left channel signal and the center channel signal aresubjected to weighting using the weight coefficients based on the Besselfunction, and the surround left channel signal is subjected to soundbeam processing, and wherein in the second array speaker arranged at theright side of the display, the right channel signal and the centerchannel signal are subjected to weighting using the weight coefficientsbased on the Bessel function, and the surround right channel signal issubjected to sound beam processing.
 4. An array speaker system accordingto claim 1, wherein a single array speaker is arranged in front of thelistener, and wherein in the array speaker, a left channel signal, aright channel signal, and a center channel signal, all of which form thefront-side channel signals, are subjected to weighting using the weightcoefficients based on the Bessel function, and a surround left channelsignal and a surround right channel signal, both of which form therear-side channel signals, are subjected to sound beam processing.
 5. Anarray speaker system including an array speaker in which a plurality ofspeaker units are arrayed in a matrix manner, wherein a first audiosignal for instructing reproduction of sound at a setup position of thearray speaker is subjected to weighting using a weight coefficient basedon a Bessel function so as to drive the speaker units, and wherein asecond audio signal for instructing reproduction of sound at a specificposition other than the setup position of the array speaker is subjectedto delay processing so as to drive the speaker units in such a way thata sound beam reaching the specific position is formed.